Trigger circuits



April 4, 1951 l. E. GROSDOFF 2,550,116

TRIGGER CIRCUITS Filed May 9, 1946 2 Sheets-Sheet l [N V EN TOR.

[ya/'5: Gram off 2 Sheets-Sheet 2 I. E. GROSDOFF TRIGGER CIRCUITS IN V EN T 0R. a/"5 @wdq f AAA 3 Susi April 24, 1951 Filed May 9, 1946 Patented Apr. 24, 1 951 UNITED "STATES :VPATE'NT OFFICE TRIGGER CIRCUITS Igor E. Grosdoff, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application May 9, 1946, Serial No. 668,442

11 Claims.

This invention relates to trigger circuits of the multivibrator type, and has for its principal object the provision of an improved trigger circuit which operates at speeds much higher than those heretofore realized in connection with circuits of conductivity is transferred from one to the other in response (1) to the application of a negative pulse to the grid of a triode element which is conducting, (2) to the application of .a positive pulse to the grid of a triode element which is not conducting, or (3) to the application of a negative pulse to the common anode terminal of the two triode elements in the case where a resistor common to both anodes is connected between the individual anode resistors and the +B lead. V

The time required for this transfer of current conductivity from one -of the triode elements to the other is dependent on the rateat which energy is stored in the grid capacitor of the conducting tri ode when a controlpulse is applied for transferring current conductivity from one of the triode elements tothe other. It has been found that this time cannot be decreased below about one'microsecond. Where higher speeds of the transfer of current conductivity are desired, it is evidently necessary to provide a path of lower impedance for charging the grid capacitor of the conducting triode element. 7

V In accordance with the present invention, this is accomplished by providing an electron discharge path through which the energy is stored in the grid capacitor more quickly. This serves to speed up the action of the trigger circuit to such an extent that current conductivity is transferred from one of the triode elements to the other in a time which is of the order of one tenth of a microsecond.

The electron discharge path through which charging of the grid capacitor is accelerated may be in the form of a triode (1) connected in shunt to the individual anode resistor of the trigger circuit so that the grid capacitor is charged through the triode and the anode resistor in parallel, or (2) connected between the anodes of the trigger circuit so that the grid capacitor is charged through the individual anode resistors in parallel and to some extent perhaps through the triode element of the trigger circuit to which current conduction is being transferred. These low impedance paths for charging the grid capacitors greatly speed up the response of the trigger circuit to the driving pulse by which current con duction is transferred from one to another of the triode elements.

The driving pulse is applied to the control grids of the triodes which are normally biased to cut oifand function to charge the grid capacitors.

The invention is applicable to many different types of apparatus such as counters where a plurality of trigger circuits are connected in cascade with one another. It is illustrated herein as applied to a high speed electronic switching device.

One important use of such electronic switching devices is the control of the application of timing pulses to an electronic counter which indicates the number of constant frequency pulses applied between opening and closing of the switch. The switch of the present invention is useful for this purpose and for numerous other purposes involving very high speed switching operations which are to be executed in a time interval of the order 7 of one-tenth microsecond or less.

The principal object of the invention is the provision of an improved trigger circuit and method of operation whereby the operating time of such a circuit is greatly reduced- Other important objects are the provision'of a high speed switch? ing device, the provision of a trigger circuit affording a low impedance path for the charging of its grid capacitors, the provision of an im-; proved high speed coupling between trigger circuits, and the provision of an improved means tion with the accompanying drawings and its scope is indicated by the appended claims.

Referring to the drawings:

Fig. 1 is a wiring diagram of a trigger circuit wherein the triodes for charging the grid capacitors have a constant bias applied to their control grids and are connected in shunt to the individual anode resistors, the driving pulses being applied only to the control grids of such triodes,

Fig. 2 illustrates a modification which difiers' from that of Fig. l in that the control triodes have a variable bias derived from the trigger circuit and the driving pulses are applied also to the control grids of the trigger circuit.

Fig. 3 is a wiring diagram of a trigger circuit wherein the triodes for charging the grid capacitors of the trigger circuit are connected between the anodes of this circuit, and,

Fig. 4 is a wiring diagram of a high speed switching device including two trigger circuits which (1) each have their anodes interconnected through a triode for discharging one of their grid capacitors and (2) are coupled together through a triode which greatly accelerates the transmission of pulses between the twov trigger circuits.

The trigger circuit of Fig. 1 includes a pair of triodes It and II. The triode 10 includes an anode [2 which is connected to the +3 lead through a resistor l3, a cathode M which is grounded, and a control grid [5 which is coupled through a capacitor It to the anode I! of the triode H. The capacitor 16 is shunted by a resistor l8 and a constant bias potential is applied to the grid l5 through a resistor IS. The triode il includes the anode H which is connected to the +13 lead through a resistor 20, a cathode 2| which is grounded, and a control grid 22 which is coupled through a capacitor 23 to the anode E2. The capacitor 23 is shunted by a resistor 24 and bias potential is applied to the grid 22 through a resistor 25.

Up to this point the connections of the trigger circuit are old and well known. It has been customary heretofore to efiect the transfer of current conduction from the triode it to the triode H and vice versa by means of a driving pulse applied directly to the grid IE or the grid 22.

In accordance With the present invention, such transfer of current conduction is effected by means of a triode 26 connected in shunt to. the resistor l3 and a triode 21 connected in shunt to the resistor 20. To this end, the triode 25 has its anode 28 connected to one terminal of the resistor l3, its cathode 29 connected to the other terminal of the resistor l3 and its control grid 39 connected through a resistor 3| and a capacitor 3 to a source of driving pulses. The triode 26 is normally biased to cut oif by a potential derived from a resistor 33 and is made conductive by a positive driving pulse applied through the capacitor 32" to the grid 30. The triode 2? has its anode 35 connected to one terminal of the resistor 28, its cathode 35 connected to the other terminal of this resistor and its control grid 37 connected through a capacitor 32 to the source of driving pulses. The triode 2'! is normally biased to cut off by a potential applied through the resistors 33 and 39 and is made conductive by a positive pulse applied through the capacitor 32. A reset switch 4| may be opened and closed to establish a standby condition with current conduction in the triode lll as indicated by the arrow.

With current conduction in the triode H] as indicated, the potential of the anode i2 is more negative due to the voltage drop of the resistor l3 and the potential of the anode l? is at substan tially +B voltage due to the relatively small current in the resistor 20. Under these conditions, the application of a positive driving pulse to the grid 31 cannot start current through the triode 21 for the reason that its anode and-cathode are at substantially the same voltage. The applica tion of a positive driving pulse to the grid 30 however, makes the triode 26 conductive so that (1) a more positive voltage is applied through the re sistor 2d to the grid 22, (2) the capacitor 23 is quickly charged, and (3) current conduction is transferred from the triode H) to the triode l I. In the same way, current is transferred from the triode II to the triode Hi. It is evident that the trigger circuit of Fig. 1 may be coupled through a capacitor 42 or a triode to a second trigger circuit for transferring a driving pulse to such second trigger circuit when current conduction is transferred from the triode I l to the triode It.

The modification of Fig. 2 is like that of Fig. 1 for the most part but differs therefrom in that the driving pulses also are applied (1) through a resistor Q3 and an adjustable part of the resistor 24 to the grid 22 of the triode I l, and (2) through a resistor 4 1 and an adjustable part of the resistor 18 to the grid l5 of the triode id. The operation of the modification of Fig. 2 is like that of the modification of Fig. l with the exception that the grids of the tubes 26 and 21 of Fig. 2 have their bias potentials changed while the trigger circuit is operating. Thus with current conduction in the tube H) as indicated by the arrow, the grid 31 is more negative than the grid 36 which provides the condition required for charging the. capacitor 23 and transferring conduction to the tube ll.

In the modification of Fig. 3, the triodes 26 and 21 for charging the grid capacitors 23 and it are connected between the anodes l2 and H of the trigger circuits. As in the previous modifications, the triodes 26 and 21 are normally biased to cut off and driving pulses may be applied to the grids 30 and 31 through a common lead or through separate leads 45 and 46. Thus the application of a positive driving pulse to the lead 35 makes the triode 26 conductive so that current is drawn through. the resistor 20, the capacitor 23. is quickly charged through the triode 26 and the resistors l3 and 2H, and current conduction is transferred from the triode ID to the triode II. The application of a positive pulse, to the lead 45 is effective in the same way to transfer current conduction from the triode II to the triode Hi.

Through the capacitor 42, the trigger circuit of Fig. 3 (as well as those of Figs. 1 and 2) may be coupled to a second trigger circuit, such coupling being made to the second circuit at the grid of the triode which does not conduct current in the standby condition of the trigger circuit.

The switch device of Fig. 4 includes two trigger circuits 41 and 48 which are coupled together through a triode 49 and are similar to the trigger circuit of Fig. 3 in several respects. Thus the trigger circuit 41 has a triode 58 connected between its anodes El and 52, and the trigger circuit 48 has a triode 53 connected between its anodes 5% and 55. The trigger circuit connections are otherwise similar to those of the trigger circuits of Figs. 1 to 3.

Thus the trigger circuit 4'! has its cathode 56 grounded, has bias potential applied from a lead 5'? through a resistor 58 to its right hand grid 59,

has bias potential applied from a lead 60 through a resistor 5| to its left hand grid 62, has its anodes 5| and '52 connected to the +3 terminal through resistors 53 and 64 respectively, has its anode 5| coupled to its grid 59 through a capacitor 65 which is shunted by 'a resistor 56 and has its anode 52 coupled to its grid 62 through a capacitor 61' which is shunted by a resistor 68.

Similarly the trigger circuit 48; has bias potential applied to its grids 69 and In through resistors H and 72, has its cathode 13 grounded, has its anodes 54 and 55 connected to the +3 lead through resistors l4 and 15, has its anode 54 coupled to its grid 78 through a capacitor i6 which is shunted by a resistor 11, and has its anode 55 coupled to its grid 69 through a capacitor 18 which is shunted by a resistor 19.

A reset switch 4! is opened and closed to estabr lish a standby condition with current conduction in the left hand triodes of the trigger circuits 4? and 48 as indicated by the arrows placed adjacent the anode resistors 63 and i4.

When the switching device including the trigger circuits 41 and 48 is open, constant frequency oscillations (indicated at 88) applied through a lead 8! to the grid 82 of a triode 83 are delivered at an output lead 84. When the switching device is closed, deliveryofthe constant frequency pulses at the output lead 84 is interrupted.

The switching device is opened in response to a positive pulse applied from a lead 85 through a capacitor 85 to the grid 81 of the triode 58 which (1) is normally biased to out off by the voltages of the resistors 38 and 89 (2) has its cathode 55 connected to the anode 54 of the trigger circuit 48, and (3) functions to couple the trigger circuit 48 to the trigger circuit 4'! so that the positive driving pulse applied to the grid 81 makes the grid 62 more negative thereby transferring current conduction from the anode 5| to the anode 52 of the trigger circuit 41.

When current conduction is transferred from the anode 5! to the anode 52, the anode 5! becomes more positive and the anode 52 more negative. The more negative potential of the anode 52 functions to light the run indicator R and to make the cathode 92 of the triode 58 more negative. The more positive potential of the anode 5! functions (1) to apply a more positive potential to the grid 95 of the cathode follower 9'5 thereby causing it to draw more current through the resistors 98 and 99 and biasing on the tube 83 so thatconstant frequency pulses (indicated at I08) are delivered at the output lead 84, (2) to make the anode 9! of the triode 50 more positive, (3) to apply through a capacitor it! to the grid I02 of the triode 53 a more positive voltage which causes the triode 53'to draw more current through the resistor '15 and to produce at the grid 89 a more negative voltage so that current conduction is transferred from the anode 54 to the anode 55.

When this occurs, there is applied from the anode 5 3 through a lead I83 and a resistor I54 to the grid 95 of the triode 58 a more positive voltage whereby the triode 50 is biased just below cut ofi.

Under these conditions, the application of a" positive stop pulse to the lead 93 makes the triode 50 conductive so that it draws more current through the resistor 53 and produces at the grid 59 a more negative voltage whereby current conduction is transferred from the anode 52 to the anode 5!. Transfer of current conduction from the anode 52 to the anode 5| 1) turns off the run indicator R and turns on the stop indicator S, and (2) biases oif the triodes 91 and 83 so that the delivery of the constant frequency pulses from the output lead 84 is interrupted.

The switching device is now in a lock out condition so that it is insensitive to driving pulses applied over the leads 85 and 93. It may be returned to its standby condition by opening and closing the reset switch 4| which functions to establish current-conduction in theanodes 5i and 54 of the trigger circuits 4! and 48.

By means of the push buttons I05 and 186, the trigger circuit 41 may be put into a run or stop condition independently of the delivery of driving pulses-over the leads 85 and 93. Thus when the push button I86 is closed, more current is drawn through a resistor [01 and the resistor 68 making the grid 62 more negative. Likewise closing of the push button I05 results in more current through the resistors 10'! and 56 and a more ne ative potential at the grid 59.

The triodes and 53, like the corresponding triodes of Figs. 1 to 3, function to speed up the action of the trigger circuits 4'! and 48 of Fig. 4. Thus when current conduction is transferred from the anode 5| to the anode 52 of the trig er circuit 41, the grid capacitor is rapidly charged through the low impedance path afforded "by the triode 58 and, when current conduction is transferred from the anode 54 to the anode 55 of the trigger circuit 48, the grid capacitor 15 is rapidly charged through the low impedance path of the triode 53. The triode 49, of course, affords a quick acting coupling between the trigger circuits 48 and M so that the negative voltage then existing at theanode 54 is applied to the grid 52 substantially instantaneously in response to the driving pulse delivered over the lead 85. As previously explained, the run and stop pulses may be applied to the grids of the tubes 50 and 49 over a single lead instead of over the separate leads and 93.

What the invention provides is a trigger cirizcuit which acts at a speed much higher than the speeds heretofore realized with trigger circuits of similar types. While the improved trigger circuit has been illustrated as applied to a high speed switching device, obviously it is applicable to electronic counters and to other types of devices involving the use of one or more trigger circuits.

I claim as my invention:

1. The combination of a trigger circuit in-' cluding a pair of triodes each having operating potential applied to its anode through a separate resistor and each having its grid coupled to the anode of the other triode through a separate capacitor, and means connected between said anodes for providing a low impedance charge path for one of said capacitors only when current conduction is transferred to the triode having said one capacitor connected in its grid circuit.

2. The combination of a trigger circuit including a pair of triodes each having operating potential applied to its anode through a separate resistor and each having its grid coupled to the anode of the other triode through a separate capacitor so that current conduction is in one or the other of said triodes, and a control triode having its cathode connected to the anode of the triode of said trigger circuit which is conducting and its anode connected to the anode of the triode of said trigger circuit which is not conducting.

3. The combination of a trigger circuit including a pair of triodes each having operating potential applied to its anode through a separate resistor and each having its grid coupled to the anode of the other triode through a separate capacitor so that current conduction is in one or the other of said triodes, a control triode having its cathode connected to the anode of the triode of said trigger circuit which is conducting and its anode connected to the anode of the triode of said trigger circuit which is not conducting, and ,means for applying to the grid of said control triode a driving pulse whereby current conduc tion is transferred from one to another triode of said trigger circuit.

4. The combination of a pair of trigger circuits. of the type wherein. a pair of triodes have opera ating potential. applied to their anodes through. separate resistors and each triode has its grid. coupled through, a capacitor to the. anode of the other triode of the pair so. that current conduction in one or .the other triode. of the pain. means for establishing current. conduction in. a predetermined triode: of. each. pair, a. coupling triodehaving. its. cathode connected to the anode of the conducting: triode. of one of. said trigger: circuits and its anode connected, to. the. anode of the: non-conducting. triode of the. other of said. trigger circuits, and; means; for applying to the grid of said. coupling triode: a driving: pulse where;- by current conduction is transferred from one triode. to. the other triode of. said. other trigger circuit.

The combination of a pair of trigger circuits of the type wherein a pair of: tricdes have: operating potential applied to their anodes through. separate resistors and each triode. has; its grid coupled through a capacitor to the anode of the. other triode of the pair so that current conduction is in one or the other triode of the pain. means for establishing. current. conduction in a predetermined triode of each pain. a coupling: triode having its cathode con-nectedtothe anode of the conducting triode of one of said trigger circuits and its anode connected to the anode of. the non-conducting triode of. the other of said trigger circuits means for applying to the. grid. ofv said coupling triode a driving pulse whereby current conduction is transferred from: onetriode to the other triode of said other trigger circuit, an output lead, and means responsive to said transfer of current conduction for initiating the delivery of pulses to said output lead;

6. The combination of a pair of trigger circuits of the type wherein a pair of triodes have operating potential applied to their anodes through separate resistors and each triode has its grid coupled through a capacitor to the anode of the other triode of the pair'so that current conduc tion is in one; or the other triode: of. the pair, means for establishing current conduction in a predetermined triode of each pair, a coupling triode. having its cathode connected to the anode of the conducting triode of one of. said trigger circuits and its anode connected. to the anode of the non-conducting triode of: the other ofsaid trigger circuits, means for applying to the grid of said. coupling triodev adriving pulse whereby current. conduction is transferred from one triode to the other triode of said other trigger circuit, and means responsive to said transfer of current conduction in said other trigger circuit for transferring current conduction in. said one trigger circuit.

'7. The combination of a pair of trigger circuits of the type wherein a pair of triodes-have operating potential applied to their anodes through separate resistors and each triode has its grid coupled through a capacitorv to the anode of the other triode of the pairv so that current. conduction is in one or the other triodeof; the: pair, means for establishing current conduction.

in a. predetermined triode of each pair; a coupling triode having its cathode connected to the anode of the conducting triode of one of said trigger circuits and its anode connected to the anode of the non-conductingtriode of theoth'er of: said trigger circuits, at. stop: triode. having. its anode and cathode respectively connected to theanode of the conducting triode and the anode of the non-conducting triode of said other trigger circuit and. its. grid. coupled to the. anode of the conducting triode of said one trigger circuit, means for applying to: the grid of said coupling triode. a driving pulse. whereby current conduction. is. transferred from one triode to the other triode of said other: trigger circuit, means. responsive to said transfer of; current conduction in said other trigger circuit-for. transferring cur.- rent' conduction in said one trigger. circuit. said stop triode, having its cathode anode potential reversed. by saidv transfer of" current conduction in. said other trigger circuit. and its grid; potential made more positive by said. transfer of current. conduction in saidone trigger circuit, means for'deliveririg. pulses to: an output lead, a. cathode; follower tube connected to control said pulse. delivering means and to beresponsive to the current conductivecondition of said stop triode, and means for applying. tothe grid of 'said stop triode a driving pulse whereby the delivery of said pulses. to said output; lead is stoppedv and current conduction is transferred in said. other trigger circuit.

8.. The combination of a pair of trigger circuits of the type whereina pair of. triodes' have operating potential applied: to: their anodes through. separate resistors and each triode has its grid coupled through a-capacitor-to the; anode of the other triode oi the pair so that current conduction is in one: or the other triode of the pair, means for establishing current conduction in a predetermined triode of eachpair, a coupling triode having its cathode connected to the anode of the conducting triode of one of said trigger. circuits. and. its anode connected to the anode of the non-conducting triode of the: other of said trigger circuits, means for applying tothe' grid. of said coupling triode a driving pulse whereby current conduction is transferred from one triode to the other triode=of said" other trigger circuit, a control triode having its cathode connected to the conducting anodeof said one trigger circuit and its. anode: connected to the other anodeof said one trigger circuit, andmeans connecting the grid of said control triode to ananode of the other trigger circuit so that saidtransfer. of current conduction. in saidother trigger circuit produces transfer ofv current conductioninsaid one trigger circuit.

9. The combination of a trigger'circuit including afirstpair of electron, discharge tubes eachhaving anode, cathode and grid electrodes, each having its anode connected to a source of operating. potential through a separate resistor and each having its grid: electrode coupled: to the anode of the other: electron discharge tube through av separate. capacitor, means to. main-- tain said trigger circuitv stable with. conduction in one or the other ofsaid' firstpair of. tubes, and 1 a second pair of electron discharge tubes having anode, cathodeandgridelectrodes each of which.

9 charge the condenser connecting the anode of said one of said first pair of tubes to the grid of the other of said first pair of tubes through said one of said second pair of tubes and to transfer conduction from said one to said other of said first pair of tubes.

10. The combination recited in claim 9 wherein each of the anodes of said second pair of tubes is respectively connected to the end of each of said separate resistors nearest said source of operating potential whereby each of said second tubes is connected across one of said separate resistors through which operating potential is applied to the anodes of said first pair of tubes.

11. The combination recited in claim 9 wherein said means to apply a bias to the grids of said second pair of tubes comprises a pair of adjustable resistors connected across each of said capacitors whereby each of said resistors is in series with the cathode of one of said second tubes and means to connect an adjustable portion of each of said adjustable resistors to the respective grid of the one of said second tubes having said other adjustable resistor in series with its cathode.

IGOR E. GROSDOFF.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Review of Scientific Instruments, November 1937, A Vacuum Tube Circuit for Scaling Down Counting Rates, by Stevenson et a1.. volume 8. pages 414-416. 

